Weik M, Ravelli R B, Kryger G, McSweeney S, Raves M L, Harel M, Gros P, Silman I, Kroon J, Sussman J L
Department of Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, NL-3584 CH, The Netherlands.
Proc Natl Acad Sci U S A. 2000 Jan 18;97(2):623-8. doi: 10.1073/pnas.97.2.623.
Radiation damage is an inherent problem in x-ray crystallography. It usually is presumed to be nonspecific and manifested as a gradual decay in the overall quality of data obtained for a given crystal as data collection proceeds. Based on third-generation synchrotron x-ray data, collected at cryogenic temperatures, we show for the enzymes Torpedo californica acetylcholinesterase and hen egg white lysozyme that synchrotron radiation also can cause highly specific damage. Disulfide bridges break, and carboxyl groups of acidic residues lose their definition. Highly exposed carboxyls, and those in the active site of both enzymes, appear particularly susceptible. The catalytic triad residue, His-440, in acetylcholinesterase, also appears to be much more sensitive to radiation damage than other histidine residues. Our findings have direct practical implications for routine x-ray data collection at high-energy synchrotron sources. Furthermore, they provide a direct approach for studying the radiation chemistry of proteins and nucleic acids at a detailed, structural level and also may yield information concerning putative "weak links" in a given biological macromolecule, which may be of structural and functional significance.
辐射损伤是X射线晶体学中一个固有的问题。通常认为它是非特异性的，表现为随着数据收集的进行，给定晶体所获得数据的整体质量逐渐下降。基于在低温下收集的第三代同步加速器X射线数据，我们发现对于电鳐乙酰胆碱酯酶和鸡蛋清溶菌酶这两种酶，同步辐射也会造成高度特异性的损伤。二硫键断裂，酸性残基的羧基失去其清晰度。高度暴露的羧基以及这两种酶活性位点中的羧基似乎特别容易受到影响。乙酰胆碱酯酶中的催化三联体残基His-440，似乎也比其他组氨酸残基对辐射损伤更为敏感。我们的研究结果对于在高能同步加速器源进行常规X射线数据收集具有直接的实际意义。此外，它们为在详细的结构水平上研究蛋白质和核酸的辐射化学提供了一种直接方法，并且还可能产生有关给定生物大分子中假定“薄弱环节”的信息，这可能具有结构和功能上的重要性。
